Compost Indoors in Winter

Outdoor composting in the North and Midwest is difficult at best. Ideally you can keep it hot by continuously “feeding” it and turning it outdoors. And when there has been just too much snow or cold, I have been content to just keep dumping greens on top of dried fall leaves to be turned in after the spring thaw. But, you can compost indoors all winter and produce a beautiful compost!

Indoor composting containers are widely available in a variety of sizes, so you can select one that suits your space as well as the amount of kitchen scraps produced by your household. And of course you can make your own container that has a tight lid as well as holes for airflow and allows for drainage with a bottom pan.

Now decide if you will aerobic compost or vermicompost. Aerobic composting requires some garden soil to provide microbes that convert organic materials into compost. Vermicomposting uses worms. The advantage with vermicomposting is it produces a compost that will help the soil retain moisture and guard against pathogens. Worms will also speed up the composting process and help aerate the bin.

SETTING UP AN AEROBIC INDOOR COMPOST

Like our outdoor compost, start with about three parts of damp brown material. If you saved some dried leaves from fall cleanup that is a great brown material. You can also use shredded newspaper (the ink is vegetable ink) or torn cardboard. Next add one part green matter which is your kitchen scraps from raw vegetables, coffee grounds, egg shells and plant clippings. No dairy, meat or bones! Mix the greens into the browns gently and sprinkle with a bit garden soil. It is important that it be soil from the ground so that it contains the microbes necessary to convert the waste to compost.

Keep your compost moist but not wet, and try to keep the ratio of browns to greens in balance. As the materials break down and you continue to add green scraps, you may need to also add more brown material. If it gets to soggy or a bit smelly you probably need more brown. Also keep the materials mixed, turning it will accelerate the decomposition. Chopping up scraps into smaller pieces will also help speed things up.

When the compost is brown and earthy it is ready for harvest. It may take 2 to 4 months to complete a compost depending on how much scrap was added and how often it was turned. Some of the newer scraps you added may not be decomposed yet, just sort those out to add to a new compost.

SETTING UP A VERMICOMPOST

Preparing a worm compost is very similar. First acquire your worms, they must be redworms on line or perhaps at a local garden center or farm supply. Do NOT use earthworms from the garden, they have to live in soil to survive. As a rule of thumb you can use a pound of redworms per square foot of compost. Keep in mind there are about a thousand red worms in a pound and the reproduce rapidly! You may want to start with a small amount of worms until you see how quickly they are consuming your scraps.

Build a bedding for the worms as above with dampened brown materials. Any cardboard should be soaked overnight to give the worms the moisture they need, but wring it out after a good soaking so that it is very damp but not dripping. Now you need some grit to help those toothless worms grind up the bedding and scraps. Sprinkle in a bit of soil, fine sand or ground up egg shells. If you included dried leaves that gives them some grit also. Now open up a bowl in the center to place the worms in, don’t just put them on top of the bedding. They need to be nestled into the moist bedding. Close up the lid and leave them alone for a week.

In the meantime, start saving your kitchen scraps. At the end of the week add in the kitchen scraps you saved and lightly trowel the scraps into the bedding. The worms will do the rest. In one week open up the compost and see how they have done with the scraps. If the worms are eating too slowly chop up the scraps next week or reduce the amount of scraps you add. As the worms multiply they should keep up better. Save up scraps and add to the bin every few days or weekly. You don’t want to over feed the worms or the bin may get a bit smelly. Check before adding scraps that the bedding is moist. If it is dry, spray mist it. If it is too wet, add more bedding.

When there is no bedding left and the bin is full of earthy compost, it is time to harvest. Typically that will take 3 to 6 months depending on how many worms are in the bin and how much you feed them. When you harvest the compost, of course you want to save your worms for the next batch. Push everything to one side of the bin, then separate any partially decomposed materials to the other side. Close up the bin for a couple of weeks and the worms will migrate to the food. Scoop out the castings and compost, then rebuild new bedding. Add the worms and residual compost. Or, dump the whole thing on a plastic sheet and let our kids pick out the worms to add to the new bedding.

Note that simply using worms with composting is not quite the same as using the more elaborate tray system for producing worm castings.